Although the present invention is related to pipe replacement in general, for purposes of simplicity, the invention is discussed herein particularly as it applies to replacement of conventional sewer pipe of the type employed in typical municipalities. The apparatus described herein is capable of grinding away or commutating most types of vitrious pipe, clay tile pipe, concrete pipe, and cast iron pipe.
Typically, sewer pipe is composed of interconnected joints of pipe composed of concrete, clay tile or metal, including cast iron, steel or ductile iron. Sections of utility pipe are typically provided with an enlarged bell at one end and a straight joining portion at the opposite end. Sections of utility pipe are placed in end-to-end relation with the straight portions thereof entering the enlarged bell of the adjacent pipe section. In the past it has been considered unnecessary to establish absolutely sealed joints when utility pipes are layed. Thus, a small amount of leakage is typical. Moreover, utility pipes, such as sewer pipes, are seldom maintained under any pressure and therefore leakage is restricted to a small amount of seepage at the pipe connections.
It has been found that utility pipes become deteriorated after having been buried for several years. It is now known that sewer gases cause deterioration of concrete material and also have an adverse effect on clay tile material and metal pipes. Upon deterioration of the pipe materials the pipes can become fractured due to shifting or settling of the earth and in some cases the joints are pulled apart, thereby allowing substantial leakage to occur at the pipe joints. It is desirable, therefore, to provide means for accomplishing replacement of utility pipes and to thereby restore the utility piping system to a substantially new condition.
In urban environments replacements of pipes such as water pipes, sewer pipes, etc. can be extremely difficult and expensive due to the presence of overlying structural features such as concrete sidewalks and driveways, tree roots, etc. In some cases, building structures may overly a buried pipe intended for replacement. It is desirable, therefore, to provide a procedure and apparatus for accomplishing efficient replacement of existing pipe such that structural features at the surface are not disturbed to any significant extent.
In many cases, the utility piping system of a municipality may have been initially established with relatively small diameter utility pipes. Additional fluid flow capacity may now be desired, such as to accommodate increased water usage or to provide for conversion of residential municipal areas for compact residential use or to provide for conversion of such areas to a large capacity commercial environment such as when large building structures or other commercialization is developed. To provide additional flow capacity needed for commercial sewer systems, it is frequently necessary to replace the entire piping system with larger pipe or to install pipes in parallel relation to the existing sewer systems. In such case excavation is usually required. It is desirable, therefore, to provide a process and apparatus for replacing existing pipes with pipes of larger dimension without significantly disturbing surface features.
Another disadvantage of conventional municipal utility systems is that the various pipe sections that are employed interfere with the efficiency of liquid flow. Each of the joints of the utility pipe in many cases constitute voids for deposit of sediment and create turbulence that interferes with efficient fluid flow. It is therefore desirable to provide a system for utility pipe replacement wherein the inside surface of the replacement pipe will be substantially free from surface discontinuities such as typically occurs in jointed utility pipe.
It has also been determined that leakage of sewage including liquid and gaseous materials into the surface earth formation can constitute severe health hazards such as pollution of surface water and shallow underground water. Leaked sewer gases can penetrate through the surface soil and collect in the residences and building structure to such extent that a health hazard becomes present. It is also desirable to provide a utility pipe replacement system wherein leak free replacement pipe is installed.
It is known that utility pipe can be fractured in situ by forcing a mandrel through existing pipe to fracture the existing pipe into multiple pipe fragments and to force the pipe fragments radially into the surrounding earth formation. In many cases the pipe fragments will be turned to present a sharp edge to the replacement pipe. Since the replacement pipe typically has a polymer composition, being formed of polyethylene, polypropylene or any one of a number of suitable polymer materials, it can be punctured or severely damaged by the sharp edges of the pipe fragments that occur as the result of a pipe fracturing operation. It is desirable, therefor, to provide a pipe replacement system wherein the existing pipe is ground to a finely comminuted form that becomes bedding material for the replacement pipe and which has no tendency to puncture or otherwise damage the replacement pipe.